The communications between a mobile terminal and a serving cell, such as the uplink communications from the mobile terminal to the serving cell, may sometimes create interference with neighbor cells. This interference may inhibit the operation of the neighbor cells or may at least cause the mobile terminal and/or the neighbor cells to operate less efficiently. In some operational states, such as a CELL_DCH state, the mobile terminal and the serving cell may monitor the neighbor cells in such a manner that instances of neighbor cell interference may be identified and the operation of the mobile terminal and/or the serving cell may be modified in such a manner as to reduce the potential for the neighbor cell interference. Indeed, in the CELL_DCH state, the neighbor cells may be added to the active set so as to be involved in uplink power control. In this regard, the mobile terminal may receive signals from the serving cell as well as the neighbor cells. As such, neighbor cells may identify instances in which the mobile terminal is creating interference such that the mobile terminal may reduce its uplink power in an effort to correspondingly reduce the neighbor cell interference. More particularly, for a mobile terminal operating in a CELL_DCH state, the uplink power from the mobile terminal may be controlled via relative grants from neighbor cells within the active set of the mobile terminal.
In other operational states, however, the mobile terminal may not communicate with the neighbor cells in the same manner and, as such, may not be able to identify instances of potential neighbor cell interference. For example, a mobile terminal in a CELL_FACH state may only receive signals from the serving cell. As such, in instances in which the mobile terminal is creating interference for the neighbor cells, the neighbor cells are unable to communicate with the mobile terminal in order to request that the power, such as the uplink power, be reduced in an effort to correspondingly reduce the neighbor cell interference. For example, in contrast to the relative grants from neighbor cells to a mobile terminal in a CELL_DCH state that serve to control the uplink power, a mobile terminal operating in the CELL_FACH state may not have similar control of its uplink power since the uplink power of the mobile terminal may only be controlled by the serving cell using absolute grants without consideration of possible neighbor cell interference. As such, a mobile terminal that is creating neighbor cell interference may impair the operation of the neighbor cells and, in some instances, may suffer from radio link failure.
In Release 8 of the Third Generation Partnership Project (3GPP) specification, an enhanced uplink for a mobile terminal in the CELL_FACH state in the idle mode was introduced. This enhanced uplink is termed a common enhanced dedicated channel (Common E-DCH). As such, mobile terminals may utilize the E-DCH in other radio resource control (RRC) states in addition to or other than the CELL_DCH state. Notwithstanding the potential for the creation of neighbor cell interference to be created by the uplink transmissions of a mobile terminal in the CELL_FACH state, it is anticipated that mobile terminals will frequently operate in the CELL_FACH state, such as to perform infrequent or bursty data transmissions, and that operation of mobile terminals in the CELL_FACH state may increase as a result of the introduction of the E-DCH. As such, the issues relating to potential neighbor cell interference while a mobile terminal is operating in the CELL_FACH state may also become more frequent and problematic.
A number of signaling based methods have been proposed in an effort to provide some measure of interference control for the neighbor cells in instances in which a mobile terminal is operating in the CELL_FACH state. However the proposals have generally suffered from various drawbacks including, for example, increased complexity for the mobile terminal and/or the serving cell or the failure to address all use cases or scenarios.